The present invention is related to an accelerated graphic port (AGP) system and the method for operating the same, and more particularly to an AGP system that supports all kinds of AGP modes and meets with all the AGP system specifications and the operating method thereof.
A typical computer system generally includes several bus systems as the interface for the peripheral devices and the host processor. In the computer system today, the PCI (peripheral component interconnect) bus is treated as a main system I/O bus for enabling the peripheral devices to proceed to data transfers with the host computer. Nonetheless, in some specific applications, such as video and 3-D graphics applications, it requires even greater throughput than PCI bus can provide. Because of the need for the increased bandwidth between the host processor and the video subsystem, the traffic on the PCI bus is becoming heavier and heavier, and the hard disk, video graphic adapter card (VGA card) and the peripheral devices are all competing for the same I/O bandwidth. In order to overcome the eventual saturation of the I/O bandwidth of the PCI bus, a new interface has been pioneered by Intel Corporation which is designed specifically for the video subsystem. It is commonly referred to as accelerated graphic port (AGP). The AGP enables the audio, video or graphic cards to efficiently make use of system memory. In particular, AGP provides a high-throughput interconnected channel for the peripheral devices such as audio, video and graphic cards to access the system memory.
With the mushroom development of the AGP technology, a variety of AGP operating modes have been addressed up to now. As indicated in FIG. 1, the differences among a variety of current AGP operating modes are listed. The configuration settings of signaling, signal swing, reference voltage, AGP operating voltage (VCCQ) and AGP slot selection for different AGP modes can be seen from FIG. 1 to get a better understanding to the characteristics of AGP systems. It is to be known from FIG. 1 that if 3.3V keyed AGP slot is selected, it can support AGP mode only; if 1.5V keyed AGP slot is selected, it can support AGP4X and AGP8X modes only, if universal AGP slot is selected, it can support AGP and AGP4x modes only. Accordingly, if it is intended to plug an AGP graphic card into a motherboard of a host computer through an AGP slot, the AGP slot can not be compatible with all kinds of AGP specifications due to the restrictions of the AGP operating modes for which the AGP slot can support.
As a result, in order to enable the antiquated AGP1X, AGP2X and AGP4X graphic cards to be compatible with the AGP8X-enabled motherboard, a universal AGP system is essential for supporting all the existent AGP system specifications, including AGP mode (AGP1X and 2X signaling), AGP4X mode (AGP1X, 2X and 4X signaling) and AGP8X mode (AGP8X signaling only), so as to eliminate the problems associated with the compatibility among different AGP system specifications.
A primary object of the present invention is to provide an AGP system which is configured so as to support all kinds of the AGP system specifications.
Another object of the present invention is to provide an AGP connector which can provide a communication channel for all kinds of AGP graphic cards to communicate with the motherboard of a host computer.
In accordance with the AGP system of the present invention, five control signals transmitted at the interface of an AGP graphic card and a motherboard are used to allow the AGP graphic card to enter into negotiation with the motherboard. These five control signals are transmitted between the AGP graphic card and the motherboard through five pins of the AGP connector, respectively. A first control signal is provided by the AGP graphic card to the motherboard for driving the voltage-switching circuit of the motherboard to generate an AGP operating voltage according to a state of the first control signal. A second control signal is provided by the system core logic of the motherboard for notifying the AGP graphic card whether or not the motherboard supports AGP8X operating mode. A third control signal is provided by the AGP graphic card to the system core logic of the motherboard for notifying the motherboard whether or not the AGP graphic card is an AGP8X graphic card. A fourth control signal is transmitted from the AGP graphic card to the motherboard for providing a first AGP reference voltage according to the AGP operating mode of the AGP graphic card for the motherboard. A fifth control signal is transmitted from the motherboard to the AGP graphic card for providing a second AGP reference voltage according to the determination of whether or not the AGP graphic card is an AGP8X graphic card for the AGP graphic card.
It is worthy to note that the motherboard can selectively generate an AGP operating voltage according to the AGP operating mode indicated by the first control signal. The resultant AGP operating voltage is used to select a first AGP reference voltage corresponding to the AGP operating mode for the motherboard. On the other hand, the motherboard can generate a second AGP reference voltage corresponding to the AGP operating mode According to the determination of whether or not the AGP graphic card is an AGP8X graphic card to the AGP graphic card.
Now the foregoing and other features and advantages in connection with the present invention will become apparent through the following descriptions with reference to the accompanying drawings, wherein: